Correlation and distinction between similar metapelite units: a geochemical approach in a case study from the Eastern Alps (Italy)
Peruzzo, Luca; Busà, Tiziana
published: Feb 26, 2001
ArtNo. ESP154017601001, Price: 29.00 €
Major and trace element geochemistry can be used in correlating or discriminating different sedimentary and volcanic rock units and their metamorphic equivalents. A geochemical study has been done on metapelites coming from four different lithostratigraphic units, showing similar petrographic features and identical metamorphic characters. They come from the boundary between the Merano-Mules and Monteneve complexes, belonging to the Austroalpine crystalline basement of the Alps. In this area, the passage from one complex to the other is not sharp and the lithostratigraphic setting is still ambiguous. Whole rock analyses (XRF and ICP-MS) were carried out on rocks sampled from four areas (B, T, M and R), along a cross-section through the boundary between the two complexes, in order to detect geochemical similarities or differences among the metapelite levels. Considering both major and trace elements as variables, chemical data have been treated by statistical analysis. Cluster analysis pointed out that rocks from the sampling area B form a well defined group with respect to the samples from the other areas. The contents of several major and trace elements, or combinations thereof, have been plotted in binary and ternary diagrams. Some of them confirm the common pelitic character of the protoliths and others clearly show systematic differences between the B group and the other samples. Chemical data have been plotted in the A-CN-K diagram to obtain information on the nature of the protoliths and on processes which may have occurred prior to metamorphism. Samples from the B group and samples from the other groups plot along two different alignments. They should represent a short part of trends corresponding to an intermediate stage of weathering of rocks derived from two different sources, and could have been affected by slight K-metasomatism.